Underground Singapore 2011 very wide range of particle size distribution (PSD) curves the data reveals thatthe material ranges between 40% and 80% fines. While the sandy OA has a tighter band of PSD curves, showing the material to be silty or clayey sand with a clay/silt content of about 20%. Table 1 shows a summary table of the geotechnical design parameters for the various soil materials encountered for this site that are used in the design of the earth retaining and support system. Table 1 Summary table of soil parameters
3 ERSS DESIGN AND PROPOSED CONSTRUCTION METHOD The schedule for completion of this project is very tight and therefore it is necessary to optimize the design of earth retaining and support system (ERSS). Contiguous Bored Pile Wall (CBP) retaining system supported by temporary ground anchorage and a top-down roof slab is proposed as the ERSS for the excavation and construction of the underground TSFB. Partial-top down construction method is adopted where the roof slab with large access opening will be cast first. Excavation will proceed and ground anchors will be installed as excavation progress downward. The use of partial top-down construction method and incorporating the roof slab as part of the support system to the excavation help to reduce one layer of temporary support system. Optimization in design of ground anchors by using high capacity ground anchor was also adopted to minimize the total number of ground anchors to be installed.
Extent of Area using Partial Top Down Construction Method
Existing viaduct piers of Bartley Flyover Figure 3 Layouts of ERSS for C937B
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